The compass in Columbus’s day existed, so far as all essentials are concerned, as it exists to-day. Although it lacked the refinements introduced by Lord Kelvin it was swung in double-cradles, and had the thirty-two points painted upon a card. The discovery of the compass, and even of the lodestone, are things wrapt in obscurity; but the lodestone had been known since at least the eleventh century, and the compass certainly since the thirteenth. With the compass were used the sea charts, which were simply maps on a rather larger and more exact scale than the land maps of the period. There were no soundings or currents marked on the old charts, which were drawn on a plane projection; and they can have been of little—practical use to navigators except in the case of coasts which were elaborately charted on a large scale. The chart of Columbus, in so far as it was concerned with the ocean westward of the Azores, can of course have contained nothing except the conjectured islands or lands which he hoped to find; possibly the land seen by the shipwrecked pilot may have been marked on it, and his failure to find that land may have been the reason why, as we shall see, he changed his course to the southward on the 7th of October. It must be remembered that Columbus’s conception of the world was that of the Portuguese Mappemonde of 1490, a sketch of which is here reproduced.
This conception of the world excluded the Pacific Ocean and the continent of North and South America, and made it reasonable to suppose that any one who sailed westward long enough from Spain would ultimately reach Cathay and the Indies. Behaim’s globe, which was completed in the year 1492, represented the farthest point that geographical knowledge had reached previous to the discoveries of Columbus, and on it is shown the island of Cipango or Japan.
By far the most important element in the navigation of Columbus, in so far as estimating his position was concerned, was what is known as “dead-reckoning” that is to say, the computation of the distance travelled by the ship through the water. At present this distance is measured by a patent log, which in its commonest form is a propeller-shaped instrument trailed through the water at the end of a long wire or cord the inboard end of which is attached to a registering clock. On being dragged through the water the propeller spins round and the twisting action is communicated by the cord to the clock-work machinery which counts the miles. In the case of powerful steamers and in ordinary weather dead-reckoning is very accurately calculated by the number of revolutions of the propellers recorded in the engine-room; and a device not unlike this was known to the Romans in the time of the Republic. They attached small wheels about four feet in diameter to the sides of their ships; the passage of the water turned the wheels, and a very simple gearing was arranged which threw a pebble into a tallypot at each revolution. This device, however, seems to have been abandoned or forgotten in Columbus’s day, when there was no more exact method of estimating dead-reckoning than the primitive one of spitting over the side in calm weather, or at other times throwing some object into the water and estimating the rate of progress by its speed in passing the ship’s side. The hour-glass, which was used to get the multiple for long distances, was of course the only portable time measurer available for Columbus. These, with a rough knowledge of astronomy, and the taking of the altitude of the polar star, were the only known means for ascertaining the position of his ship at sea.
The first mishap occurred on Monday, August 6th, when the Pinta carried away her rudder. The Pinta, it will be remembered, was commanded by Martin Alonso Pinzon, and was owned by Gomaz Rascon and Christoval Quintero, who had been at the bottom of some of the troubles ashore; and it was thought highly probable that these two rascals had something to do with the mishap, which they had engineered in the hope that their vessel would be left behind at the Canaries. Martin Alonso, however, proved a man of resource, and rigged up a sort of steering gear with ropes. There was a choppy sea, and Columbus could not bring his own vessel near enough to render any assistance, though he doubtless bawled his directions to Pinzon, and looked with a troubled eye on the commotion going on on board the Pinta. On the next day the jury-rigged rudder carried away again, and was again repaired, but it was decided to try and make the island of Lanzarote in the Canaries, and to get another caravel to replace the Pinta. All through the next day the Santa Maria and the Nina had to shorten sail in order not to leave the damaged Pinta behind; the three captains had a discussion and difference of opinion as to where they were; but Columbus, who was a genius at dead-reckoning, proved to be right in his surmise, and they came in sight of the Canaries on Thursday morning, August 9th.